Communication method and communication apparatus

ABSTRACT

The problem is to facilitate alteration of a transmission line in the case where the target device establishes a connection on the bus and thereby secures a transmission line in order to transmit stream data in a network of the IEEE 1394 scheme or the like. Stream data outputted from an output device  1  connected to a predetermined network is received by an input device  2 . When the output device or a different device has sent an order for setting so that output data of the output device  1  may be inputted to a data input section  2   b  of the input device  2 , the input device  2  conducts input setting based on the order. In addition, when the device which sent the order has sent an order to cancel the input setting, the input device  2  conducts processing of canceling the input setting.

This application is a continuation of U.S. Pat. No. 7,050,449application Ser. No. 09/764,565 filed Jan. 17, 2001, the entirety ofwhich is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication method and acommunication apparatus which are applied to the case where datacommunication is conducted between devices connected by a bus line of,for example, the IEEE 1394 scheme.

2. Description of the Related Art

AV devices capable of mutually transmitting information via a networkusing a serial data bus of the IEEE 1394 scheme have been developed.When conducting data transmission via this bus, there are prepared anisochronous transfer mode to be used when video data and audio data of acomparatively large capacity are subject to real time transmission, andan asynchronous transfer mode to be used when still images, text data,control commands and so on are transmitted certainly. A dedicated bandis used for transmission every mode.

FIG. 18 is a diagram showing an example of connection using a bus of theIEEE 1394 scheme. It is now assumed that a source device “a” which is adevice for sending out data, a target device “b” which is a device forreceiving data sent out from the source device “a”, and a controller “c”for controlling data transmission between the devices “a” and “b” areconnected to a bus “d” of the IEEE 1394 scheme. Assuming at this timethat video data is transmitted between the devices “a” and “b” under thecontrol of the controller c, the controller c secures an isochronoustransfer channel on the bus “d”, establishes connection between thedevices “a” and “b”, and starts transmission from the source “a” to thetarget device “b”.

In the case where data transmission is thus conducted between the sourcedevice “a” and the target device “b”, a transmission scheme of controlcommands called AV/C command transaction set which can be applied to,for example, AV devices can be applied. Details of the AV/C commandtransaction set are opened to the public at an Internet web site.

Considering data transmission of video data and audio data from thesource device to the target device, selection of data which can beinputted to an input device can be conducted freely, if input selectioncan be conducted on the target device side. Therefore, the presentinventors proposed earlier processing of establishing a connectionbetween the target device and the source device and securing atransmission line on the bus (Japanese Patent Application 11-328764).

SUMMARY OF THE INVENTION

Basically, in the IEEE 1394 scheme, only a device which established aconnection can cancel the connection. If the target device establishes aconnection, other devices such as the source device and the controlleron the bus cannot execute processing of canceling the connection. Evenin the case where it is desired to start data transmission between otherdevices on the bus, the controller must wait until the connectionestablished by the target device is canceled if there is no free line inthe transmission lines. There occurs such a problem that it becomesimpossible for the controller to conduct transmission control on the busaccurately.

An object of the present invention is to facilitate alteration of atransmission line in the case where the target device establishes aconnection on the bus and thereby secures a transmission line in orderto transmit stream data in a network of the IEEE 1394 scheme or thelike.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of a system configurationaccording to an embodiment of the present invention;

FIG. 2 is a block diagram showing an example of an internalconfiguration of an IRD according to an embodiment of the presentinvention;

FIG. 3 is a block diagram showing an example of an internalconfiguration of a video deck according to an embodiment of the presentinvention;

FIG. 4 is a block diagram showing an example of an internalconfiguration of a television set according to an embodiment of thepresent invention;

FIG. 5 is a diagram showing an example of a cycle structure of datatransmission on a bus of the IEEE 1394 scheme;

FIG. 6 is a diagram showing an example of connection using a bus of theIEEE 1394 scheme;

FIG. 7 is a diagram showing an example of a configuration of datatransmitted by using an AV/C command transaction set;

FIG. 8 is a diagram showing example of commands and responses of an AV/Ccommand transaction set;

FIG. 9 is a diagram showing an example of an input select controlcommand according to an embodiment of the present invention;

FIG. 10 is a diagram showing examples of a subfunction according to anembodiment of the present invention;

FIG. 11 is a diagram showing an example of an output plug according toan embodiment of the present invention;

FIG. 12 is a diagram showing an example of a signal destination plugaccording to an embodiment of the present invention;

FIG. 13 is a diagram showing a different example of a signal destinationplug according to an embodiment of the present invention;

FIG. 14 is a diagram showing an example of an input select controlresponse according to an embodiment of the present invention;

FIG. 15 is a diagram showing examples of status data according to anembodiment of the present invention;

FIG. 16 is a diagram showing an example of an input plug according to anembodiment of the present invention;

FIG. 17 is a diagram showing an example of processing according to anembodiment of the present invention; and

FIG. 18 is a configuration diagram showing an example of a networksystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the present invention, stream data outputted from anoutput device connected to a predetermined network is received by aninput device. When the output device or a different device has sent anorder for setting so that output data of the output device may beinputted to a data input section of the input device, the input deviceconducts input setting based on the order. In addition, when the devicewhich sent the order has sent an order to cancel the input setting, theinput device conducts processing of canceling the input setting.

According to the present invention, it becomes possible to cancel theinput setting when a cancel order is received from the device which sentan order to execute input setting, after an input device executed theinput setting.

Hereafter, an embodiment of the present invention will be described byreferring to FIGS. 1 to 17.

A configuration example of a network system to which the presentinvention has been applied will now be described by referring to FIG. 1.It is assumed that a plurality of devices are connected to this networksystem via a serial data bus 9 of the IEEE 1394 scheme. Here, as shownin FIG. 1, an IRD (Integrated receiver decoder: digital satellitebroadcast receiving device) 1, a video deck 2, and a television set 3are connected to the bus 9. Each of the devices is a device havingterminals for connection to a bus of the IEEE 1394 scheme, and has afunction mounted thereon to effect control by using the AV/C commandtransaction set. Here, the television set 3 has a function of acontroller (control device) serving as a device for effectingtransmission control on the bus 9. Furthermore, another device such asthe IRD 1 connected to the bus 9 may have the function serving as thecontroller. Furthermore, a device other than AV devices, such as apersonal computer device, is connected to the bus 9 in some cases.

When viewed from the viewpoint of the functions prescribed in the AV/Ccommand transaction set, the devices 1, 2 and 3 may have a configurationhaving a subunit for executing processing of implementing each functionand a plug section for conducting data inputting and outputting betweenthe bus 9 and the internal subunit. For example, the IRD 1 has a tunersubunit 1 a for receiving the broadcast, the video deck 2 has a tapesubunit 2 a for recording information onto a recording medium (e.g., avideo tape) and reproducing information from a medium, and thetelevision set 3 has a control section 3 a for executing a controlfunction. Furthermore, the devices 1, 2 and 3 have the plug sections 1b, 2 b and 3 b, respectively. In each of the plug sections 1 b, 2 b, and3 b, a plurality of plugs are mounted and can be connected to aplurality of channels on the bus 9. Relations between the plugs and thechannels will be described later. In a transmission example describedlater, the IRD 1 is handled as a source device serving as a data outputdevice, the video deck 2 is handled as a target device serving as a datainput device, and the television set 3 is handled as a controllerserving as a control device.

FIG. 2 shows an example of an internal configuration of the IRD 1. TheIRD 1 is a digital satellite broadcast receiver. Signals received by aconnected antenna 101 are subject to reception processing in a tuner102. A broadcast wave of a predetermined channel is thus received. Thesignal received by the tuner 102 is subject in a de-scramble circuit 103to processing of canceling scramble applied to broadcast data. The datawith the scramble canceled are supplied to a data separation section104. Desired data is extracted from data multiplexed into one channel.

Video data separated by the data separation section 104 is supplied toan MPEG video decoder 105, and subject therein to decode processing ofthe MPEG scheme. Then a resultant signal is supplied to a digital toanalog converter 106 to produce an analog video signal. The analog videosignal is supplied to an output terminal 107. Audio data separated bythe data separation section 104 is supplied to an MPEG audio decoder108, and subject therein to decode processing of the MPEG scheme. Then aresultant signal is supplied to a digital to analog converter 109 toproduce an analog audio signal. The analog audio signal is supplied toan output terminal 110.

Furthermore, the IRD 1 of the present example has an IEEE 1394 interfacesection 111 so as to be able to send out the received video data andaudio data of the MPEG scheme onto the connected bus 9. Furthermore,when the IRD 1 has received various data broadcast channels or audiodata channels, the IRD 1 can also send out the received data onto thebus 9 via the IEEE 1394 interface section 111.

The reception operation and operation of sending data onto the bus 9 areexecuted under the control of a central control unit (CPU) 112.Furthermore, data sending from the IEEE 1394 interface section 111 tothe bus 9 and data receiving from the bus 9 in the interface section 111are also executed under the control of the CPU 112. A memory 113 forstoring data required for the control is connected to the CPU 112.

FIG. 3 shows an example of an internal configuration of the video deck2. The video deck 2 is a video recording and reproducing device of adigital scheme for recording video data (and audio data accompanying thevideo data) on a medium such as magnetic tape as digital data coded bythe MPEG scheme and reproducing the video data.

As shown in FIG. 3, the video deck 2 has such a configuration thatmagnetic tape mounted on a cassette 201 which is a casing made of resinis subjected to recording and reproducing using a magnetic head attachedto a rotary head drum section 202. A signal reproduced by the magnetichead of the rotary head drum section 202 is supplied to a recording andreproducing system circuit 203 and processed. Reproduced data of theMPEG scheme is thus obtained and decoded by an MPEG decoder 204 torestore original digital data. The restored digital video data isconverted to an analog video signal by a digital to analog converter205. Then, the analog video signal is outputted via an analog outputterminal 206 and supplied to a monitor and the like connected to theterminal 206. Furthermore, digital video data decoded by the MPEGdecoder 204 is outputted from a digital output terminal 207. Inaddition, reproduced data supplied to the MPEG decoder 204 can besupplied to an IEEE 1394 interface section 212 and sent out to theconnected bus 9 as video data coded by the MPEG scheme and left intact.

As for the configuration of a recording system, an analog video signalobtained at an analog input terminal 208 is converted to digital videodata by an analog to digital converter 209. Then the converted videodata is supplied to an MPEG encoder 210. The MPEG encoder 210 producesvideo data coded according to the MPEG scheme. The video data codedaccording to the MPEG scheme by the MPEG encoder 210 is supplied to therecording and reproducing system circuit 203 and processed. A recordingsignal to be supplied to the rotary head drum section 202 is thusobtained. This recording signal is recorded on magnetic tape mounted onthe cassette 201. Furthermore, as for video data of the MPEG schemesupplied from the bus 9 to the IEEE 1394 interface section 212 as well,the video data is supplied to the recording and reproducing systemcircuit 203 via the MPEG encoder 210 and recorded onto magnetic tapemounted on the cassette 201.

The reproduction operation and recording operation in these circuits areexecuted under the control of a central control unit (CPU) 213.Furthermore, data sending from the IEEE 1394 interface section 212 tothe bus 9 and data receiving from the bus 9 in the interface section 212are also executed under the control of the CPU 213. A memory 214 forstoring data required for the control is connected to the CPU 213. Asfor the cassette 201 mounted on the video deck 1 of the present example,it is a cassette having a non-volatile memory 215 attached thereto insome cases. When the cassette having the non-volatile memory 215attached thereto is mounted, the CPU 213 manages reading and writing ofdata stored in the memory 215. Index information (such as the recordingdate, channel, and program) and the like of data recorded on themagnetic tape is stored in the memory 215.

The configuration of the television set 3 will now be described byreferring to FIG. 4. FIG. 4 shows an example of the internalconfiguration of the television set 3. Here, the television set 3 isformed as the so-called digital television set for receiving the digitaltelevision broadcast. An input terminal 301 having an antenna or thelike connected thereto is connected to a tuner 302. Reception processingis conducted in the tuner 302 to receive a broadcast wave of apredetermined channel. The signal received by the tuner 302 is subject,in a de-scramble circuit 303 as occasion demands, to processing ofcanceling scramble applied to broadcast data. The data with the scramblecanceled are supplied to a data separation section 304. Desired data isextracted from data multiplexed into one channel.

Video data separated by the data separation section 304 is supplied toan MPEG video decoder 305, and subject therein to decode processing ofthe MPEG scheme. Then a resultant signal is supplied to a digital toanalog converter 306 to produce an analog video signal. The analog videosignal is supplied to a received image processing circuit 307.Processing for driving display means 309 such as a cathode ray tube anddisplaying an image is thus conducted. It is also made possible tosupply video data obtained at an external input terminal 308 to thereceived image processing circuit 307 and conduct display processingtherein.

Audio data separated by the data separation section 304 is supplied toan MPEG audio decoder 310, and subject therein to decode processing ofthe MPEG scheme. Then a resultant signal is supplied to a digital toanalog converter 311 to produce an analog audio signal. The analog audiosignal is supplied to a sound processing circuit 312. Processing fordriving a speaker 314 is conducted therein, and the sound is outputtedfrom the speaker 314. It is also made possible to supply audio dataobtained at an external input terminal 313 to the sound processingcircuit 312 and conduct display processing therein.

Furthermore, the IRD 1 of the present example has an IEEE 1394 interfacesection 321 so as to be able to send out the video data, audio data, andthe like of the MPEG scheme or the like received by the tuner 302 ontothe connected bus 9. Furthermore, video data and audio data transmittedvia the bus 9 can be supplied to the decoders 305 and 310 via the dataseparation section 304, and video image receiving and audio outputprocessing can be conducted.

These operations as the television set and the transmission operationvia the bus 9 are executed under the control of a central control unit(CPU) 322. Data sending from the IEEE 1394 interface section 321 to thebus 9 and data receiving from the bus 9 in the interface section 321 arealso executed under the control of the CPU 322. The function as acontroller for managing the transmission on the bus 9 is also executedby the CPU 322. Therefore, the CPU 322 and its peripheral circuitcorrespond to the control section 3 a in the television set 3 shown inFIG. 1. A memory 323 for storing data required for the control isconnected to the CPU 322. Furthermore, although not illustrated, thereare provided manipulation keys for ordering various manipulationsconcerning the television set and manipulations concerning operations ofother devices connected by the bus 9 (such as the input switchoveraction, recording operation, reproduction operation, and so on), and areceiving section for receiving similar manipulation orders from remotecontrol devices. Control based upon the manipulation order is executedby the CPU 322.

A data transmission state on the bus 9 of the IEEE 1394 schemeconnecting the above described devices to each other will now bedescribed. FIG. 5 is a diagram showing a cycle structure of datatransmission of devices connected by the IEEE 1394. According to theIEEE 1394, data is divided into packets and the packets are transmittedin a time division manner by taking a cycle having a length of 125 μs asa reference. This cycle is produced by a cycle start signal suppliedfrom a node having a cycle master function (some device connected to thebus). Isochronous packets secure a band (which is called band althoughit is a time unit) required for transmission from the head of everycycle. In isochronous transmission, therefore, transmission of data in afixed time is ensured. If a transmission error occurs, there is nomechanism for protection and data is lost. During time of each cyclewhich is not used for isochronous transmission, a node which has securedthe bus as a result of arbitration sends out asynchronous packets. Inthis asynchronous transmission, reliable transmission is ensured byusing acknowledgment and retry. However, the transmission timing doesnot become fixed.

In order that a predetermined node (device) may conduct isochronoustransmission, the node must correspond to the isochronous function. Inaddition, at least one of nodes corresponding to the isochronousfunction must have a cycle master function. In addition, at least one ofnodes connected to the IEEE 1394 serial bus must have an isochronousresource manager function. The device having the isochronous resourcemanager function corresponds to the above described controller (thetelevision set in the case of the present example).

FIG. 6 is a diagram showing relations among plugs, plug controlregisters, and isochronous channels required to conduct datatransmission on a bus. AV Devices 11 to 13 are connected by an IEEE 1394serial bus. Isochronous data specified in channel by an oPCR [1] amongoPCR [0] to oPCR [2] prescribed in transmission rate and the number ofoPCRs by an oMPR of the AV device 13 is sent out to a channel #1 of theIEEE 1394 serial bus. Between iPCR [0] and iPCR [1] prescribed intransmission rate and the number of iPCRS by an iMPR of the AV device11, the iPCR [0] specifies the input channel #1. The AV device 11 readsisochronous data sent out on the channel #1 of the IEEE 1394 serial bus.In the same way, the AV device 12 sends out isochronous data onto thechannel #2 specified by the oPCR [0]. The AV device 11 reads isochronousdata from the channel #2 specified by the iPCR [1].

It is set so that data sent out from an output plug of a device of thedata transmission source onto the bus may be received by an input plugof a device of data receiving destination by using the channel thussecured. Processing of thus setting a channel and a plug andestablishing a connection is executed under the control of apredetermined device controller) connected to the bus.

In this way, data transmission is conducted between devices connected bythe IEEE 1394 serial bus. In the system of the present example, however,control and state decision of respective devices can be conducted byutilizing an AV/C command prescribed as commands for controlling devicesconnected via the IEEE 1394 serial bus. Data used in this AV/C commandwill hereafter be described.

FIG. 7 shows a data structure of a packet transmitted in an asynchronoustransfer mode of the AV/C command. The AV/C command is a command set forcontrolling an AV device, and its CTS (ID of command set)=“0000”. AV/Ccommand frames and response frames are exchanged between the nodes. Inorder to prevent casting a burden upon the bus and the AV device, aresponse to a command is defined to be sent within 100 ms. As shown inFIG. 7, data of an asynchronous packet has 32 bits (=1 quadlet) in thehorizontal direction. Upper columns of FIG. 7 show a header portion ofthe packet, and lower columns of FIG. 7 show a data block. A destinationID indicates the destination.

The CTS indicates an ID of the command set. In the AV/C command set,CTS=“0000”. A c type/response field indicates a function class of acommand when the packet is a command, and a processing result of acommand when the packet is a response.

Commands are broadly divided into four kinds: (1) commands (CONTROL) forcontrolling the function from the outside; (2) commands (STATUS) forinquiring about the state from the outside; (3) commands for inquiringwhether support of a control command is present, from the outside(GENERAL INQUIRY (whether support of an opcode is present) and SPECIFICINQUIRY (whether support of an opcode and operands are present)); and(4) commands (NOTIFY) for requesting the notice of a state change to theoutside.

A response is returned according to the command kind. As responses tothe CONTROL commands, there are “NOT IMPLEMENTED”, “ACCEPTED”,“REJECTED” and “INTERIM” (interim response). As responses to the STATUScommands, there are “NOT IMPLEMENTED”, “REJECTED”, “IN TRANSACTION”, and“STABLE”. As responses to “GENERAL INQUIRY” and “SPECIFIC INQUIRY”commands, there are “IMPLEMENTED” and “NOT IMPLEMENTED”. As responses tothe “NOTIFY” command, there are “NOT IMPLEMENTED”, “REJECTED”,“INTERIM”, and “CHANGED”. Commands and responses other than thosedescribed here are defined in some cases.

A “subunit type” is provided to specify a function in the device. Forexample, “tape recorder/player”, “tuner”, or the like is assigned. Inorder to distinguish in the case where there are a plurality of subunitsof the same kind, addressing is conducted by using a subunit id as adistinguishing number. An “opcode” represents a command. An “operand”represents a parameter of the command. “Additional operands” is a fieldadded as occasion demands. “Padding” is a also field added as occasiondemands. A “data CRC” (Cyclic Redundancy Check) is used for error checkat the time of data transmission.

FIG. 8 shows a concrete example of the AV/C command. FIG. 8(A) showsconcrete examples of c type/response. Its upper column shows commandsand its lower column shows responses. “CONTROL” is assigned to “0000”.“STATUS” is assigned to “0001”. “SPECIFIC INQUIRY” is assigned to“0010”. “NOTIFY” is assigned to “0011”. “GENERAL INQUIRY” is assigned to“0100”. “0101 to 0111” are reserved and secured for futurespecifications. “NOT IMPLEMENTED” is assigned to “1000”. “ACCEPTED” isassigned to “1001”. “REJECTED” is assigned to “1010”. “IN TRANSITION” isassigned to “1011”. “IMPLEMENTED/STABLE”is assigned to “1100”. “CHANGED”is assigned to “1101”. “INTERIM” is assigned to “1111”. “1110” isreserved and secured for future specifications.

FIG. 8(B) shows concrete examples of the subunit type. “Video Monitor”is assigned to “00000”. “Disk recorder/Player” is assigned to “00011”.“Tape recorder/Player” is assigned to “00100”. “Tuner” is assigned to“00101”. “Video Camera” is assigned to “00111”. “Vender unique” isassigned to “11100”. “Subunit type extended to next byte” is assigned to“11110”. “Unit” is assigned to “11111”, and it is used when the commandor response is sent to the device itself. For example, turning on andoff of the power supply can be mentioned.

FIG. 8(C) shows concrete examples of opcodes. For each of the subunittypes, a table of opcodes exists. In FIG. 8(C), opcodes in the casewhere the subunit type is the “tape recorder/player” are shown.Furthermore, for each opcode, an operand is defined. Here,“VENDOR-DEPENDENT” is assigned to “00h”. “SEARCH MODE” is assigned to“50h”. “TIMECODE” is assigned to “51h”. “ATN” is assigned to “52h”.“OPEN MIC” is assigned to “60h”. “READ MIC” is assigned to “61h”. “WRITEMIC” is assigned to “62h”. “LOAD MEDIUM” is assigned to “C1h”. “RECORD”is assigned to “C2h”. “PLAY” is assigned to “C3h”. “WIND” is assigned to“C4h”.

By utilizing the AV/C command transaction set thus prescribed, controlof the devices connected to the bus is conducted and data transmissionbetween devices connected by the bus is conducted on the basis of thecontrol. In the present example, there are prepared a command forcontrolling the input selection state and a canceling command forcanceling the input selection executed by the control, with respect toinput devices (target devices) to which stream data can be inputted. Apacket of the command is sent out by either an output device foroutputting pertinent stream data, or a control device for controllingthe transmission between the output device and the input device.However, the canceling command can be outputted by only a device whichissued a command for executing the input selection to be canceled by thepertinent command.

FIG. 9 shows a data configuration example of [opcode] and [operand] ofan input select control command which is this command. This data isdisposed in a packet shown in FIG. 7. Its command type becomes [CONTROL]because the command is data for giving a control order. In the area ofthe [opcode], data of [INPUT SELECT] which is the pertinent command isdisposed. In the area of the [operand (0)], data of a subfunctionshowing details of the control state is disposed. In the area of the[operand (1)], a section of bits 1 to 4 (a portion denoted by“reserved”) is undefined and specific data (here, a value F which is“1111”) is disposed in a section of bits 5 to 8 in order to indicatethat the area is an area which is not used in the command.

In the area of [operand (2) and operand (3)], a node ID of an outputdevice is disposed. In the area of [operand (4)], an output plug ID ofthe output device is disposed. By the node ID and the output plug ID ofthe output device, an output device (source device) desired to outputthe stream data and an output plug of the device are specified.

In the area of [operand (5)], an input plug ID of an input device isdisposed. In the area of [operand (6) and operand (7)], data concerninga subunit which is an internal function block of the input device isdisposed. To be concrete, in the area of [operand (6)], data concerningthe type of a destination subunit which is a subunit of the input deviceside and data of the subunit ID are disposed. In the area of [operand(7)], data of an input plug of the destination subunit is disposed. Whenthe area of the [operand (6)] has a specific value (such as data FF),however, there results an order which does not specify the subunit ofthe input device. The area of [operand (8)] is undefined here.

In the case where the input plug ID of the input device is not known atsuch a stage that a device sending this command (i.e., the output deviceor the control device) sends the command, data of, for example, amaximum value is disposed. In the output plug ID of the output device,ID data of a plug for outputting stream data from the output device isdisposed.

FIG. 10 shows an example of subfunction data showing details of thecontrol state disposed in the area of the [operand (0)]. Here, thefollowing four subfunctions are defined.

When the value is “0”, the subfunction is a subfunction of [Connect] andthe command is a command for ordering establishment of connection withrespect to the output device.

When the value is “1”, the subfunction is a subfunction of [Path change]and the command is a command for conducting a path change in the casewhere device selection has been conducted. This path change is, forexample, a change from a path (transmission line) using the bus 9 to ananalog transmission line, or an opposite change.

When the value is “2”, the subfunction is a subfunction of [select] andthe command is a command for conducting the selection of the outputdevice, but causing a wait in such a state that the processing ofestablishing a connection to the device is not conducted.

When the value is “3”, the subfunction is a subfunction of [disconnect]and the command is a command for disconnecting the connectionestablished with respect to the output device. This command correspondsto a command for causing canceling to be executed.

FIG. 11 is a diagram showing a data configuration example of an outputplug ID. For example, 31 output plugs for serial bus of [0] to [30] and31 external output plugs of [0] to [30] are provided with individualIDs. The external output plugs are plugs which do not use the bus 9. Aportion denoted as “Reserved” is a data value which is undefined in plugID.

FIG. 12 shows a data example of an input plug ID of the destinationsubunit in the area of the [operand (7)]. The example of FIG. 12 is anexample of the case where the area of [operand (6)] becomes data FF andthe destination subunit is not specified. In this example, 31 inputplugs for serial bus of [0] to [30] and 31 external input plugs of [0]to [30] are provided with individual IDs. Furthermore, in the case ofdata 7F, it orders to use one of input plugs of such a kind as to beused for the serial bus, and it does not specify an input plug amongthem. Furthermore, in the case of data FF, it orders to use one of inputplugs of such a kind as to be used for external input, and it does notspecify an external input plug among them. A portion denoted as“Reserved” is a data value which is undefined in plug ID.

FIG. 13 shows a data example of an input plug ID of the destinationsubunit in the area of the [operand (7)] in the case where the area of[operand (6)] is other than the data FF (i.e., in the case where adestination subunit is specified). In this case, IDs individuallyprovided to 31 subunits of [0] to [30] are used. Furthermore, in thecase of data FF, it orders not to specify an input plug of the subunit.A portion denoted as “Reserved” is an undefined data value.

When the packet of the command heretofore described and shown in FIG. 9is transmitted to an input device, a response to the control command isreturned to the transmission source of the command by the input device.FIG. 14 shows a data configuration example of [opcode] and [operand] ofan input select control response serving as the response. This data isdisposed in a packet shown in FIG. 7. In the area of the [opcode], dataof [INPUT SELECT] which is a pertinent command are disposed. In the areaof [operand (0)], data of the subfunction showing details of the controlstate is disposed. As for the data of the subfunction, data of thecommand is returned as it is. In the area of [operand (1)], a section ofbits 1 to 4 (a portion denoted as “reserved”) is here undefined, andstatus data (result status) which is data concerning the execution stateof an order specified via the command by the input device is disposed inthe section of bits 5 to 8.

In the area of the [operand (2)] and subsequent operands, data disposedin the control command are basically disposed and returned as they are.When the data is data which orders only the kind of the plug and whichdoes not specify the plug, as the value of the input plug ID or thedestination plug ID, however, the ID of the input plug (or thedestination plug) assigned by the input device is disposed and returned.

The status data [result status] indicating the state of the input devicedisposed in the fifth to eighth bits of the section of the [operand (1)]is here defined, for example, as shown in FIG. 15. When this status datais used, there are [REJECTED] for rejecting the order of the command and[INTERIM] for returning an interim response, besides [ACCEPTED] forabiding by the order of the command, as response types. For each ofresponse types, a plurality of status data values are set.

FIG. 15 will be described in order from the top. In the case of theresponse of [ACCEPTED] for abiding by the order of the command, thefollowing two data are prepared.

1. [no error] data

data indicating that the order of the command has succeeded

2. [ready] data

data indicating that connection has completed in such a state thatstream data can be inputted within the input device, but a wait state iscaused due to some cause

In the case of the response [REJECTED] for rejecting the order of thecommand, the following eight data are prepared.

1. [disabled] data

data indicating that there is set such a mode as to inhibit inputsetting in response to an order from another device

2. [locked] data

data indicating that the operation of the input device is locked due tosome cause (such as in the middle of sound recording) and input settingcannot be conducted

3. [p-to-p] data

data indicating that there is no room in the input plug and a connectioncannot be established because there is a connection established underthe control from another device

4. [insufficient resource] data

data indicating that a connection cannot be established because there isno room in the band (channel) on the bus

5. [source not found] data

data indicating that a specified output plug of the output device(source device) cannot be found

6. [not selected] data

data indicating that a specified path cannot be established. This datais used when a path change is specified and the change to the pathcannot be conducted.

7. [not registered] data

data indicating that a specified path is registered. This data is alsoused when a path change is specified and there is not the specifiedplug.

8. [any other reason] data

data at the time when the order is rejected for another reason.

Furthermore, in the case of the response of [INTERIM] which is aninterim response to the command, the following two data are prepared.

1. [no information] data

data transmitted temporarily when a response cannot be given within atime (for example, 100 ms) prescribed by the AV/C command transactionset because of some reason.

2. [busy] data

data transmitted temporarily when a response cannot be given within atime (for example, 100 ms) prescribed by the AV/C command transactionset because of some reason. When this data is received, it can be judgedthat the normal state is restored after elapse of a predetermined time(for example, 10 seconds).

FIG. 16 shows a data example of an input plug ID disposed in the case ofa control response. For example, 31 plugs for serial bus of [0] to [30]and 31 external output plugs of [0] to [30] are provided with individualIDs. Furthermore, IDs which can be defined in the future are prepared.Here, data of the maximum value FF is not used in the case of theresponse [ACCEPTED] for abiding by the order of the command.

An example of transmission processing using the input select commandhaving the configuration heretofore described will now be described byreferring to FIG. 17.

In this example, the IRD 1 is used as the output device (source device)of stream data. Video data and audio data received by the IRD 1 are sentout onto the bus 9. Furthermore, as the input device (target device),the video deck 2 for recording the video data and audio data transmittedfrom the IRD 1 is used. Here, the order of the transmission is issued bythe television set 3 which is a control device on the bus.

It is now assumed that the control for making the video deck 2 recordbroadcast data (video data and audio data) of a specific channelreceived by the IRD 1 is conducted by the television set 3 on the basisof manipulation or the like within the television set 3. At this time,the control device television set 3) sends the input select controlcommand to the input device (the video deck 2) (step S11), and sends anorder for requesting the connection management so that data outputtedfrom the output device (IRD 1) may be received by the input device. Inthis control command, the subfunction becomes [Connect] for giving anorder to establish the connection (see FIG. 10).

At this time, the video deck 2 which is the input device completesinternal connection processing of connecting a tape subunit which is aninternal function block to an input plug. In addition, the video deck 2conducts processing of making the IRD 1 which is an output deviceestablish a point to point (P to P) connection for connecting bothdevices and securing a transmission line on the bus (step S12). Whenthis connection is established, the video deck 2 returns a response of[ACCEPTED] indicating comprehension of the order of the control commandto the television set 3 which is the transmission source of the inputselect control command (step S13).

When the processing heretofore described is conducted, for example, theIRD 1 causes video data and audio data to be sent out on the securedtransmission line on the bus. The video deck 2 receives the data andsupplies the received data to the tape subunit in the video deck 2, andconducts processing of recording the data on a recording medium(videotape).

It is now assumed that a request to cancel the connection between theIRD 1 and the video deck 2 has occurred in the television set 3 servingas the control device because of some reason. At this time, thetelevision set 3 sends the input select control command for cancelingthe pertinent connection to the video deck 2 (step S14). In this controlcommand, the subfunction becomes [disconnect] for ordering disconnectionof the connection (see FIG. 10).

When the video deck 2 has received the control command having the[disconnect] as its subfunction, a CPU in the video deck 2 executesprocessing of canceling the P to P connection between the video deck 2and the IRD 1 (step S15). After the cancel processing has been executed,the video deck 2 returns a response of [ACCEPTED] indicating that theconnection is canceled to the television set 3 serving as the controldevice (step S16).

In this way, the pertinent connection is canceled by sending a commandfor canceling the connection executed on the basis of a command sent bythe control device to the input device on the bus. In the case where theinput device manages the P to P connection, therefore, it becomespossible to cancel the connection from a device other than the inputdevice. It becomes possible to conduct various controls, such as achange of the output device, efficiently on the basis of an order of adevice having a control function, such as the television set.

In this case, only the control device which issued a request toestablish connection is adapted to be able to issue an order to cancelthe connection. Therefore, a different device on the bus does not cancelthe connection. Accordingly, the transmission line setting state on thebus does not become confused.

In the example, heretofore described, the connection setting andcanceling are executed according to an order from a control device (thetelevision set 3) which is different from the output device (IRD 1).Alternatively, it is also possible that, for example, the output deviceincorporates the control function and the connection setting andcanceling are executed according to an order from the output device.

In the above described embodiment, the processing in the case wherevideo data and audio data are transmitted on the bus has been described.The embodiment can be applied to control used when various other streamdata are transmitted on the bus. Furthermore, the output device and theinput device may be devices other than those of the above describedexample.

Furthermore, in the above described embodiment, the case of the networkincluding the bus of the IEEE 1394 scheme has been described. However,the embodiment can be applied to the case where similar datatransmission is conducted between devices of a different networkconfiguration.

Furthermore, in the above described embodiment, the function ofconducting the above described processing is set in each device.Alternatively, it is also possible that a program for executing similarprocessing is distributed to users by using some provision medium and auser mounts a program stored in the medium on a computer device or thelike connected to a bus (such as a bus of the IEEE 1394 scheme) toexecute the similar function. The provision medium in this case may be amedium provided to users via communication means such as Internet,besides a physical recording medium such as an optical disk or amagnetic disk.

According to the present invention, it becomes possible to cancel inputsetting when a cancel order is received from the device which sent anorder to execute the input setting, after an input device executed theinput setting. Even if such a configuration that only the input devicecancels data transmission setting is adopted, therefore, it becomespossible to cancel the setting for data transmission by only sending acancel order to the input device, so long as the order is issued by adevice which caused the setting to be executed. Efficient utilization oftransmission bands on the bus thus becomes possible.

In this case, the input setting order is made an order to specify aninput plug of the input device. Therefore, input setting processing withan input plug in the input device specified and its cancel processingbecome possible. It becomes possible in such a state that an input plugis specified to certainly conduct the input setting and its canceling.

Furthermore, the specified input plug specifies only a kind of the plug.Data specifying the plug subjected to input setting is obtained on thebasis of a response from the input device. And the canceling order ismade an order for canceling input setting of a plug specified by thedata. Even if the state of the input plug of the input device is notknown, therefore, it becomes possible for the device which orders theinput device to conduct input setting, to send an order to execute theinput setting. Furthermore, when canceling the input setting, a specificplug is specified. Therefore, it becomes possible to certainly cancelonly the setting connected by a necessary plug.

Furthermore, a plug of an internal function block of the input device isalso specified. As for the plug of the internal function block of theinput device, therefore, specified input setting processing and itscancel processing become possible.

Having described preferred embodiments of the present invention withreference to the accompanying drawings, it is to be understood that thepresent invention is not limited to the above-mentioned embodiments andthat various changes and modifications can be effected therein by oneskilled in the art without departing from the spirit or scope of thepresent invention as defined in the appended claims.

1. A communication method of receiving stream data outputted from anoutput device connected to an IEEE 1394 network, in an input device,wherein: when said output device or a different device has sent an orderfor setting so that output data of said output device is inputted to adata input section of said input device, said input device conductsinput setting based on said order; and when said device which sent saidorder has sent an order to cancel said input setting, said input deviceconducts processing of canceling said input setting; wherein said inputsetting order is an order to specify an input plug of said input device;and wherein a plug of an internal function block of said input device isalso specified.
 2. A communication apparatus connected to an IEEE 1394network, characterized in that said communication apparatus comprises:input and output means for conducting communication with another devicein said network; and communication control means responsive to detectionof an order to enable reception of stream data from a predetermineddevice, out of data received by said input and output means, forconducting input setting of the stream data, and responsive to detectionof an order to cancel the input setting issued by the same device asthat which issued the order to enable reception of stream data, in astate with the input setting conducted, for conducting processing tocancel said input setting, wherein the input setting executed undercontrol of said communication control means is setting for inputtingsaid stream data from an input plug specified by the detected order,wherein the input setting executed under control of said communicationcontrol means is setting for supplying said stream data to a plug of aninternal function block specified by the detected order.